XD-500 In cases where a trigger does not exist upon Job Deployment, the Rest Interface needs to hand back a 404 exception vs. a 500 exception.  Also added constants for string values.
As a second note I thinned out the exception stack that is returned is more concise.
Per Code Review reduced the accessiblity the parser and messageSender of parent class.
XD-500 Return a 400 error instead of 404 if the named trigger associated with this job has not been created.

This is per Eric's update to the story.